Page 1 of 4 123 ... LastLast
Results 1 to 15 of 54

Thread: M2 diy passive crossover thread ---- from down under

  1. #1
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409

    M2 diy passive crossover thread ---- from down under

    Reading on from post ................

    This is a new thread dedicated to a DIY Passive Crossover for the M2 DIY clone

    Its a lead in starter for anyone planning an M2 clone or those wishing to simplify from an active to a passive set up.
    This is not a completing alternative to the DSP crossover specified by JBL.

    I will continue to post some measurement as a means of zeroing in on the passive crossover network.

    Today I measured the 2430 driver on the M2 horn withe the voice coils wired in parallel.
    The acoustic response is compared to the 2216dn in a grouped screen shot.

    The test conditions are identical to my previous measurements:

    The DBFS reference test level for the REW Analyster was set at 75db.
    Distance = D = 1 metre


    Notes:

    The purpose of today’s measurements was to ascertain the difference in sensitivity of the parallel wiring of the 2430 driver voice coils.

    Based the the curves below the 2430 driver with its voice coils wired in parallel is between 10-12 db more sensitive than the 2216nd.

    Back in post 859 of the M2 diy thread l noted with the 2430 driver voice coils wired in series (32 ohms ac impedance) the 2216nd woofer was about 5 db less sensitive.

    So what’s the deal?

    There are advantages and disadvantages with wiring the voice coils either way. In a dsp scenario there will be 6 db less noise due to the lower driver sensitivity.

    In a passive crossover the additional sensitivity of the 2430 can be used to an advantage in the passive network for matching the sensitivity to the 2216nd woofer after normalising the 2430 response.

    For example when using dual 2216nd woofers.

    The down size is that the lower driver impedance can present a lower load impedance to the power amp at high frequencies unless care is taken.
    Attached Images Attached Images    

  2. #2
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    To repeat from the M2 diy thread these are the steps l am following.

    I hope to have the test and measure series below sorted by mid next week.

    I have received a REW file a the 2451 with SL diaphragm from Scott and compared it with my REW measurements of the 2430 driver. While the are similar the emphasis for EQ normalisation below the mass roll off point is different. I also need to compare and assess the sensitivity differences.
    I will discuss this in more detail once l have collected the data from steps B to E.

    My next steps are :

    A. To assess parallel connection of the 2430 driver voice coils and some measurements. Done
    B. Test and measure a 2447 driver on the M2 horn.
    C. Build and tests the 2216nd 6th order passive filter.
    D. Validate 2447- versus 2430 measurements and HF filter design.
    E. Build and test HP filter& EQ or any revisions for different drivers.
    F. Test and measure passive system voltage drivers and frequency response curves.
    G. Subjective assessment. Yes/No Pass. Fail revert to E.

    I hope to have cut panels for the M2 enclosures soon.

  3. #3
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Update

    Some promising news. I have been able to adapt different driver impedances from 32 ohm to 5.7 ohms using the 2340 in either series or parallel voice coil connection.

    No RCL elements in the crossover need changing.

    The Tilt Adjustments work beautifully after l optimised the network impedances. See last image. The red line is the overall flat optimisation including crossover slope @ 36 db per octave.

    Range of the Presence Tilt Control is just over 1db in the 1.4khertz to 2.5 hertz region. The effect is most noticeable on brass instruments.
    Range of the Brilliance Tilt Control is 3.3db at 10,000 hertz. The rate is about 1 db per octave referenced to 2Khertz. The effect is to arrive at a comfortable HF tonal balanced when using CD horns.

    The network has yet to be fully tested. Simplified High Pass section shown only.

    I am happy with the network at this stage. My wife always said l was very clever…Bom Bom…Lol

    Hi Robert H. If you can please email me an export file of your 476 impedance and FR files from Leap for comparison. l can then check the results of a JBL conventional driver with a 12 ohm working impedance. The email address is in my signature.

    The Doctor
    Attached Images Attached Images      
    Last edited by Ian Mackenzie; 06-15-2022 at 08:47 AM. Reason: Typos

  4. #4
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    7,801
    Hello Ian

    Sure working now send them latter on.

    Rob
    "I could be arguing in my spare time"

  5. #5
    Senior Member srm51555's Avatar
    Join Date
    May 2013
    Location
    Wisconsin
    Posts
    598
    Hi Ian,

    Thanks for posting the 1m measurements on the 2216nd's. I don't recall these posted anywhere here. What was the cabinet volume?

    Thanks,
    Scott

  6. #6
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Hi Scott,

    The test enclosure is 5 cu ft3 was built from the plans in the JBL enclosure kit in the late 1970ís.

    Itís a semi free field test as the enclosure is on its side about 1.2m off the ground outside.

    The M2 horn was carefully positioned above the woofer.

    Another empty test enclosure was vertically positioned to supporting the test enclosure.

  7. #7
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Here is my previous loudspeaker tester Tilly. I miss her.

    Isn’t she beautiful. Okay

    There's nothing serious about this thread. Its diy.
    Attached Images Attached Images  

  8. #8
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Speed Bumps and why they are there?
    For those looking at the bumps in the horn response around 1.5Khertz do not be put off.

    The divisions are 5 db so it’s a variation of like +-1.5 db and the response at your listening position with have far more artefacts.

    Always trust your ears with a familiar recording.

    Do not listen with your eyes by interpreting a frequency response and then listening.

    The reason for the bumps is the variation in the voltage drop across the Presence tilt resister connected directly to the compression driver via the crossover filter. Further treatments of the response would add complexity and cost. I also prefer not to put EQ close to the crossover region which is phase sensitive. It’s a trade off of having the access and convenience of a variable adjustment in the frequency range. I think the benefits out way any potential disadvantages.

    Future permanent modifications
    If after a time a user reaches a consensus on the Presence Tilt setting (l can make the range of this control wider) a modification can be used to make a permanent response level with obvious bumps.

    In the scheme of things these curves are only 1/6 octave smoothed for clarity. The pitting of an un smoothed response makes a curve unnecessarily noise for public viewing. Why look at every wrinkle of the Mona Lisa when you won’t see it at your listening position some 2.5. to 2.3 metres back.

    Listening Window Response
    Once the network is finalised l will run some listening window averaged curves over a 60 degree arch.
    Attached Images Attached Images  

  9. #9
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    7,801
    Hello Ian

    Check your email. Sent you the files for both of my 476Mg's on the M2. I also have IMP files for both the 476Mg and the 2453HSL on the PTH1010. Let me know if you want them. It gives 8 vs 16 ohm drivers on the same waveguide to use for comparison if you want them.

    Rob
    "I could be arguing in my spare time"

  10. #10
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Hi Rob,

    I received the files thank you. Interesting.


    I also need to compare a conventional compression drivers response to the 2430. If you can send a FR file of the 0476 on the M2 that would be great thanks.

  11. #11
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    There is consistency in the shape of the impedance curves. The magnitude is of course different.

    For those viewing this thread the reason for the comparisons is to assess the best approach for implementing a universal passive crossover and passive CD EQ for several different compression drivers on the M2 horn.

    I still need to confirm the low end response of the 2451 / or an 0476 in comparison to the 2430 on the M2 horn.

    It might end up a modular section of crossover filter and or EQ as a build for different drivers. I am looking for a more universal approach if possible. That will depend on the impedance and response variations.

    I have been able to obtain a tighter response within +- 1 db on the horn at a granular level with dedicated EQ. This is best arranged for a specific driver.

  12. #12
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Taking loudspeaker measurements always outside always gathers the attention of onlookers.
    Attached Images Attached Images  

  13. #13
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Hi Rob,

    In case you are interested I have looked into installing Leap 5 in a new machine with my XP PC becoming more ancient with the future potential of failure like my AT PC.

    A local supplier has offered to install Windows 7 Ultimate with legal XP emulation in a new Mac Pro. So Leap will run in a virtual XP environment. My existing Mac Pro is a 2016 so l will kill two birds with one stone. I prefer the Mac environment and it links to my other Apple devices.

    I think they will install Parallels or similar.

    The portability of Leap 5 means l can crunch the data on move or while travelling as well as mobility for measurements.
    Ian

  14. #14
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    7,801
    Quote Originally Posted by Ian Mackenzie View Post
    Hi Rob,

    I received the files thank you. Interesting.


    I also need to compare a conventional compression drivers response to the 2430. If you can send a FR file of the 0476 on the M2 that would be great thanks.

    Sure I have several have to figure out the ones I used vs threw out. If I am not mistaken more robust low end on the standard 4" drivers.

    Rob

    So is that lizard as big as it looks??
    "I could be arguing in my spare time"

  15. #15
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Hi Rob,

    The lizard is about 18-24 inches long.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Passive Monitor Thread
    By Robh3606 in forum Lansing Product DIY Forum
    Replies: 165
    Last Post: 03-13-2021, 11:55 AM
  2. passive crossover JBL 077
    By nfbertone in forum Lansing Product Technical Help
    Replies: 13
    Last Post: 08-08-2012, 02:06 AM
  3. Need help with passive crossover!!
    By rbrandt73 in forum Lansing Product DIY Forum
    Replies: 3
    Last Post: 07-05-2007, 11:43 AM
  4. Passive crossover JBL
    By alnico in forum Lansing Product General Information
    Replies: 4
    Last Post: 10-06-2004, 08:44 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •